Universität zu Köln

Edelmann, Hans G. . Plant root development: is the classical theory for auxin-regulated root growth false? Protoplasma. WIEN: SPRINGER WIEN. ISSN 1615-6102

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Abstract

One of the longest standing theories and, therein-based, regulation-model of plant root development, posits the inhibitory action of auxin (IAA, indolylacetic acid) on elongation growth of root cells. This effect, as induced by exogenously supplied IAA, served as the foundation stone for root growth regulation. For decades, auxin ruled the day and only allowed hormonal side players to be somehow involved, or in some way affected. However, this copiously reiterated, apparent cardinal role of auxin only applies in roots immersed in solutions; it vanishes as soon as IAA-supplied roots are not surrounded by liquid. When roots grow in humid air, exogenous IAA has no inhibitory effect on elongation growth of maize roots, regardless of whether it is applied basipetally from the top of the root or to the entire residual seedling immersed in IAA solution. Nevertheless, such treatment leads to pronounced root-borne ethylene emission and lateral rooting, illustrating and confirming thereby induced auxin presence and its effect on the root - yet, not on root cell elongation. Based on these findings, a new root growth regulatory model is proposed. In this model, it is not IAA, but IAA-triggered ethylene which plays the cardinal regulatory role - taking effect, or not - depending on the external circumstances. In this model, in water- or solution-incubated roots, IAA-dependent ethylene acts due to its accumulation within the root proper by inhibited/restrained diffusion into the liquid phase. In roots exposed to moist air or gas, there is no effect on cell elongation, since IAA-triggered ethylene diffuses out of the root without an impact on growth.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Edelmann, Hans G. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-562158
DOI:	10.1007/s00709-021-01697-z
Journal or Publication Title:	Protoplasma
Publisher:	SPRINGER WIEN
Place of Publication:	WIEN
ISSN:	1615-6102
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language GRAVITROPIC DIFFERENTIAL GROWTH; ACID-GROWTH; GRAVISTIMULATED ROOTS; MEDIATED GROWTH; ETHYLENE; COLEOPTILES; TRANSPORT; INHIBITION; ELONGATION; REDISTRIBUTION Multiple languages Plant Sciences; Cell Biology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/56215